AIM: To evaluate, in young adults, the effect of different preventive programmes on oral hygiene and to determine whether the variables investigated are predictors of gingival health. MATERIAL AND METHODS: This randomized, blinded, parallel, controlled clinical study examined the effectiveness of three dental health programmes. Four hundred subjects aged 20-27 years, 211 males and 189 females, participated in the study. They were recruited from a Public Dental Service clinic and from a private dental practice in Jönköping, Sweden. The effect of the programmes on plaque and gingivitis was evaluated over a 3-year period. The programmes included activities that were adapted for individuals as well as for groups. The plaque indices (PLI) and gingival indices (GI) were used to evaluate the programmes. RESULTS: All programmes resulted in a decrease in PLI and GI. The greatest decrease was found in the group that was followed-up every 2 months. Professional tooth cleaning was non-significant for the clinical result. Gingival health at baseline, participation in any of the test programmes, and knowledge of the dental diseases caries, gingivitis or periodontitis were significant predictors of good gingival health. CONCLUSIONS: The study confirms the efficacy of three different preventive programmes in reducing supragingival plaque and gingival inflammation. Professional tooth cleaning provided no clinical benefit beyond that derived from individual and group-based health education.